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Atmosfera
Centro de Ciencias de la Atmosfera de la Universidad Nacional Autonoma de Mexico
Atmosfera

Centro de Ciencias de la Atmosfera de la Universidad Nacional Autonoma de Mexico

0187-6236

Atmosfera/Journal AtmosferaSCI
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    Thermodynamic simulation of the seasonal cycle of temperature, pressure and ice caps on Mars

    Victor M. MENDOZABlanca MENDOZARene GARDUNOGuadalupe CORDERO...
    24页
    查看更多>>摘要：We present a thermodynamic model to simulate the atmospheric temperature and pressure, the regolith temperature and the polar CO_2 ice caps vertical thickness and horizontal extent of Mars. This is done using the temperatures of the atmosphere and regolith for each Martian day of the year, determined from the thermodynamic equation. Assuming a CO_2 atmosphere, we calculate its emission spectrum using the spectral calculator E-Trans with the HITRAN database (E-Trans/HITRAN), resulting in only a band at 15 mm and the rest transparent, through which the radiation emitted by the regolith and ice caps (considered as black bodies) goes toward space. We also include the solar radiation extinction and longwave emission of atmospheric dust. The equation calculates the energy balance between the absorbed solar radiation and the outgoing longwave radiation, incorporating also the latent heat released by CO_2 condensation, the sensible heat flux from the surface to the atmosphere, the latent heat flux due to the CO_2 ice sublimation and the heat exchange between the surface regolith layer and its lower layers. The atmospheric planetary scale horizontal turbulent heat transport is parameterized with an exchange coefficient, which is an order of magnitude smaller than that employed in the terrestrial troposphere. Considering a long-time average, the regolith vertical temperature profile is explicitly found using the thermal inertia including conductivity; its temperature regulation is achieved through the thermal conduction from the surface during the warm season. This stored energy goes back to the surface during the cold season. Our model simulates the seasonal variation ofthe polar ice caps and consequently of the surface atmospheric pressure through the CO_2 mass balance between them. Finally, it is explicitly shown that the amplitude of the global seasonal pressure cycle is modulated by a local thermal-orographic effect, which increases (decreases) this amplitude in the low
      原文链接:
    • NSTL
    • Centro Ciencias Atmosfera Unam

    Evaluation of clearness index and cloudiness index using measured global solar radiation data: A case study for a tropical climatic region of Nigeria

    Olanrewaju Olukemi SONEYE
    15页
    查看更多>>摘要：This study uses a two-year dataset (January 2016-December 2017) on global solar radiation to model the clearness and cloudiness indices at Ile-Ife, Nigeria, a tropical location. Analysis of the daily variations showed that most days at the location are uniform in cloudiness, with scarcely any day either extremely cloudy or extremely clear. On a monthly basis, the clearness index ranged from 0.27 to 0.51, while cloudiness index ranged from 0.44 to 0.72, confirming that the variations of both ratios are influenced by changes in the position of the sun, turbidity and clouds. The seasonal variations of the two parameters were observed to be inverse, so that increases in the clearness index induced by cloudless sky and dry months correspond to decreases in the cloudiness index values and vice versa. The minimum values (0.10 and 0.28) of the clearness index at the location are observed to be higher than the minimum value of 0.05 stipulated for the clearness index in cloudy conditions. Two empirical equations for estimating the maximum clearness index in terms of the average clearness index and the cloudiness index in terms of the clearness index are developed and recommended for other locations with climatological conditions similar to those of the study site. It was furthermore observed from the evaluation of formulated empirical equations that the Hollands and Huget and the Saunier et al. models performed well and improved by about 23.62 and 3.66%, respectively, after calibration, to make the models suitable for their application at other tropical areas.
      原文链接:
    • NSTL
    • Centro Ciencias Atmosfera Unam

    Preliminary study of soot and polycyclic aromatic hydrocarbons in emitted particles from adobe kilns that use scrap tires as fuel

    Brenda L. VALLE-HERNáNDEZEstheisy LóPEZ-BELLOMiguel TORRES-RODRIGUEZCecilia AGAPITO-ABRAHAM...
    17页
    查看更多>>摘要：Artisanal pottery in Mexico is largely manufactured in handmade adobe kilns using scrap tires as main fuel in rural and periurban areas, making this activity one of the main sources of atmospheric pollutants. An intensive sampling campaign was conducted in a Mexican small town in order to characterize the toxic species emitted by more than 400 adobe kilns working in two scenarios: low and normal activity, as well as to determine their carcinogenic potential. PM10 concentrations ranged 50-80 μg m~(-3) and 77-290 μg m~(-3) during low and normal activity periods, while PM_(2.5) concentrations were 33-57 μg m~(-3) and 37-177 μg m~(-3) in the same periods. Organic carbon and elemental carbon presented concentrations around four and seven times greater, respectively, during a normal activity period than during a low activity period in both particle sizes. Quantified polycyclic aromatic hydrocarbons were twice greater during the normal activity period than during the low activity period. Carcinogenic PAHs accounted for 53-59% of total PAHs in all cases and the carcinogenic potential (B[a]Peq) in PM_(10) during the normal activity was 25 times higher than the European Commission recommendation, proving thereby the high risk that nearby population faces to those emissions.
      原文链接:
    • NSTL
    • Centro Ciencias Atmosfera Unam

    Is the energy balance in a tropical lowland rice paddy perfectly closed?

    Dibyendu CHATTERJEEChinmaya KUMAR SWAINSumanta CHATTERJEEPratap BHATTACHARYYA...
    20页
    查看更多>>摘要：A two-year (2015 and 2016) field experiment was carried out to study the surface energy budget and energy balance closure (EBC) in a tropical lowland rice paddy in Cuttack, India. Maintenance of a standing water layer in lowland irrigated rice ecosystem makes it unique and this strongly influences the surface energy balance which may alter the surface runoff, ground water storage, water cycle, surface energy budget, and possibly microclimate of the region. To study this, an experiment was conducted using eddy covariance system to measure the surface energy balance components during two cropping seasons (dry season, DS and wet season, WS) and two consecutive fallow periods (dry fallow, DF and wet fallow, WF). The rice was grown in puddled wet lands in DS and WS and the ground was left fallow (DF and WF) during the rest of the year. Results displayed that daily average latent heat flux at surface (LE) and at canopy height (LEc) dominated over sensible heat flux at surface (H) and canopy height (Hc), respectively due to the presence of water source coming from the standing water in the rice field. The EBC was evaluated by ordinary least square (OLS), energy balance ratio (EBR) and residual heat flux (RHF). In OLS,the slope ranged 0.38-0.89 (2015) and 0.28-0.99 (2016) during the study period. Average RHF was 10.3-12.0% higher in WS as compared to DS. It was concluded that the EBC estimated using RHF is the most suitable way to calculate closure for lowland rice paddy since it can distinguish different seasons distinctively, followed by OLS. Much variation was not observed in EBR after inclusion of storage terms (water, soil, photosynthesis, canopy) to the classical EBR.
      原文链接:
    • NSTL
    • Centro Ciencias Atmosfera Unam

    Investigating the performance of SWAT and IHACRES in simulation streamflow under different climatic regions in Iran

    Abazar ESMALIMohammad GOLSHANAtaollah KAVIAN
    18页
    查看更多>>摘要：It is often reported that simpler models, due to their low parameter requirements, perform better than more complex models. To test this, the current study compared a simple rainfall-runoff model (IHACRES) with a complex watershed model (SWAT). Based on these two approaches, six models were developed for three climatically distinct (arid, semi-arid and semi-humid) watersheds in Iran. The coefficient of determination (R~2) and the Nash-Sutcliffe model efficiency coefficient (NS) were calculated in each case. In arid, semi-arid, and semi-humid watersheds the SWAT model (R~2 = 0.52, 0.68, 0.66; NS = 0.54, 0.63, 0.64, respectively) outperformed the IHACRES model (R~2= 0.37,0.70,0.57; NS = 0.22,0.57, 0.56, respectively) for the same respective climate zones. Overall, SWAT performed better than IHACRES, although both models had acceptable performances in the semi-arid and semi-humid watersheds. In the arid watershed, the IHACRES model performed poorly compared to SWAT.
      原文链接:
    • NSTL
    • Centro Ciencias Atmosfera Unam

    Influence of Santa Ana winds on the surface circulation of Todos Santos Bay, Baja California, Mexico

    Ana Laura FLORES-MORALESLuis Felipe NAVARRO-OLACHERuben CASTROReginaldo DURAZO...
    13页
    查看更多>>摘要：The influence of easterly and northeasterly dry and warm Santa Ana winds (SAw) on the surface circulation of Todos Santos Bay, Mexico, is studied from surface currents and wind data measured during the most extreme periods of activity (autumn-winter season). Sea surface currents were measured using a system of coastally-based HF radar stations between 2009 and 2015. Winter-mean surface circulation showed a cyclonic tendency. Atmospheric variables allowed the grouping of ~122 SAw events, 23% of which caused a noticeable change in the background circulation. Event-mean current patterns showed dissimilar responses to the acting winds, with some SAw events driving weak offshore currents, another that developed an eddy-pair circulation inside the bay, and one rather intense (winds of 8-10 m s~(-1)) that developed a clockwise circulation overturning the cyclonic long-term winter-mean. In general, changes in the circulation were related to an offshore transport of surface waters into the open ocean.
      原文链接:
    • NSTL
    • Centro Ciencias Atmosfera Unam

    Parametric study of hurricanes intensity as they move over land

    Daniel PASTRANACesar TREVINO
    10页
    查看更多>>摘要：Two of the most important tropical cyclone parameters, which are used as a measure of their intensity, are the maximum surface wind speed (local parameter) and the pressure difference between the free atmosphere and the pressure in the center of the storm (global parameter). In this paper we reexamined the relationship between these parameters via the Euler number, which is a nondimensional parameter that relates the overall pressure difference to the dynamic pressure generated by the maximum value of the wind speed. The calculations were performed all along the track of 20 tropical cyclones using the National Hurricane Center's extended best track database for the Atlantic basin. It was found that when the cyclone is over water, the Euler number tends to remain constant, while over land the parameter varies drastically with a tendency to grow. These results confirm that over sea, when they have reached hurricane strength, tropical cyclones evolve slowly remaining near the steady state, highlighting the importance of transient states during strong dissipation. The Euler number seems to be independent of the global warming.
      原文链接:
    • NSTL
    • Centro Ciencias Atmosfera Unam

    Analysis and selection of optimal sites for wind farms: case study, region north of Mexico

    Alejandro RUVALCABA GARCIATomás GONZALEZ MORáN
    11页
    查看更多>>摘要：The analytic hierarchy analysis process allowed establishing a hierarchical model of a target function under a set of criteria aimed at choosing the best sites for the installation of wind farms in the north of Mexico. In this study, a large number of known and estimated criteria of diverse types (technical, economic, environmental, and social) were used, based on preliminary studies and information that allowed for the identification of the most relevant variables. The process simplifies a complex problem into simpler ones that can be analyzed independently, facilitating the efforts of decision takers since it allows envisaging the feasible alternatives. Once the most weighty and relevant variables were obtained, each variable was transformed into feasibility maps, and through the technique of map algebra coupled to a geographic information system, the sites were assessed in feasibility percentages in a general map fulfilling the set of imposed variables. The best scenarios for the location of a wind farm corresponded to the southern part of the state of Coahuila. The multicriteria analyses focused on decision-making within the planning process and characterization of feasible sites for a wind farm, are tools that optimize the selection of different variables, favoring the most relevant for the project by considering decision elements that are difficult to assess or quantify.
      原文链接:
    • NSTL
    • Centro Ciencias Atmosfera Unam